The elegant demonstration by Milkovich et al that graft and multi-branched copolymers can be prepared by the copolymerization of macromonomers (hereafter "macromers" for brevity), with conventional small monomers has initiated a spate of publications in this field. Particular interest has been focussed upon the radical polymerizations of vinyl monomers because it was expected that the rate of polymerization and the degree of polymerization on the molecular weight (Mn) of the growing polymer may be substantially the same as that of conventional vinyl monomers. Both the rate and the degree of polymerization are generally quite high for vinyl monomers which are therefore of major economic interest. The realization that a large moiety adjacent the vinyl head group often reduces the rate of polymerization of the macromer because of the relatively low concentration of reactive end groups, particularly at high conversions where also the increased viscosity of the reaction mass reduces the diffusion of the macromer to the reaction site, has done nothing to dull this interest.
The particular interest of this invention is to prepare graft copolymers containing high glass transition temperature (T.sub.g) grafts, having a T.sub.g above 100.degree. C., such graft copolymers being heretofore unknown. Though all the polymers (`polymacromers`) prepared herein are graft copolymers, the term "comb-like" or "comb" is used to refer to those in which a graft (or `tine`) is present at regular intervals spaced by a single repeating unit in the backbone of the comb. More particularly, the polymacromers of this invention are derived from a polymerizable polyarylene polyether macromer, referred to herein as a PAPE (for brevity) macromer.
A PAPE macromer typically has a diphenyl sulfone, dinaphtyl sulfone, diphenyl ketone, dinaphtyl sulfone, diphenyl ketone, or, 2,6-dimethyl phenylene repeating unit.
A typical PAPE macromer has a Mn in the range from about 1000 to about 10,000, and because of this relatively low mol wt are referred to herein as OH-terminated oligomers. They are typically terminated at the other chain end with a halogen (Hal) atom, though such Hal termination is not essential for the functionalization of the oligomers' OH group. It is the OH-group which I have functionalized to contain a single vinyl group, hence the macromers formed are said to be vinyl-functionalized. These macromers may be thermally or otherwise polymerized to form comb-like polymers by homopolymerization of a vinyl-functionalized macromer; and graft copolymers by copolymerization of two or more vinyl-functionalized macromers. All the graft homopolymers and copolymers are thermally stable at a temperature above 100.degree. C.
Most commonly, an anionic living polymer is reacted with electrophiles containing unsaturated functions. For example, polystyrene, polyisoprene, or styreneisoprene diblock macromers have been terminated with various polyfunctional groups such as alpha-olefin, vinyl alkyl ether, styryl, acrylate, methacrylate, maleic half ester, or epoxy. Macromers have also been synthesized by Tsuruta by a poly-addition reaction of divinyl compounds (Makromol. Chem. 183 29-45, 1981), and by Hudecek by transformation of reactive polymer end groups (Polym. Bull. 3 143, 1980).
Cationic techniques have also been used for preparing macromers by Kennedy et al (1980) who prepared a polyisobutylene macromer, and by Sierra-Vargas (1980) who prepared a polytetrahydrofuran macromer.
Of more particular interest is that it is known that it is possible to use a wide variety of macromers with one polymerizable vinyl head group, each of which macromers may be tailored in Mn and structural configuration to provide polymers with a wide spectrum of physical properties. Typical of such macromers are those with styryl and acrylate head groups disclosed by Kennedy, J. P. et al in I.U.P.A.C. Intl. Symp. on Macromolecules, Florence, Preprints, p 162 (1980); Polym. Prepr. Am. Chem. Soc. Div. Polym. Chem., 23, No. 2, 99 (1982); Polym. Bull., 6, 135 (1981); inter alia.
The use of a direct reaction of a polysulfone oligomer having a terminal phenyl group, in solution (referred to as an "in solution reaction"), has been found appropriate to provide the macromer with a single terminal vinyl group which group is a residue of an .alpha.,.beta.-monoolefinically unsaturated acyl halide. Except that it must be borne in mind that the reaction produces a strong acid (typically HCl when an acyl chloride is used) which immediately inhibits the reaction. As a result, carrying out the reaction to obtain more than a 50% yield is a problem.
Where the reactants are poorly soluble in commonly available organic solvents, phase transfer catalysis ("PTC") has been used, both in polymer modification (see J. M. J. Frechet, Polym. Prepr., 23(1), 139 (1982); and, Y. Imai, J. Macromol. Sci. -Chem., A15, 833 (1981)), and in polymer synthesis (see L. J. Mathias, J. Macromol. Sci. -Chem., A15, 853 (1981); and, F. L. Cook and R. W. Brooker, Polym. Prepr., 23(1), 149 (1982)). In nucleophilic displacement step-growth polymerizations in which PTC syntheses have been used, not only can the need for anhydrous aprotic solvents be obviated but there are also several other advantages. The reaction is very fast, quickly reaching high MW and 100% yield. The polymer weight is relatively independent of the ratio between the nucleophilic and electrophilic reactants. Most importantly, the organic-soluble polymer obtained almost always contains an electrophilic species as a chain end, independent of the reaction yield and reactant ratio.
I have found that this approach, namely a phase transfer catalyzed (PTC) reaction, is surprisingly effective where an alkali metal phenolate of a mono-OH-terminated PAPE does not react easily with a m-or p- haloalkyl vinylaromatic reactant such as chloromethylstyrene ("ClMS"), or, haloalkyl olefinically unsaturated reactant, each of which are referred to herein as "HAR".
Further, it must be kept in mind that a reaction with ClMS at relatively higher temperature than room temperature will result in polymerization of the ClMS and the reaction is therefore unsuitable. Prepolymerization is also a problem, though to a lesser extent, with an esterification reaction with a haloacyl reactant. Even when carried out below about 20.degree. C., the reaction mixture contains a low molar concentration of phenol end groups which are less reactive than the nonsolvated onium phenolate and consequently inhibits the reaction. As a result, carrying out this reaction to obtain more than 50% yield is a problem.
Still further, an alkali metal salt of a phenol-terminated polysulfone lacks stability under conventional PTC reaction conditions, particularly using a minor mol equiv amount of PTC, and hydrolyzes. This invention provides a solution to the problem.
None of the prior art teachings relate to a OH-terminated aromatic polyether sulfone (APS) or a polyether ketone (APK), or a polyphenylene oxide (PPO) macromer which is etherified with a vinylbenzyl ("VB") group (also referred to as `monostyrenated`); nor do the teachings relate to such a macromer which is esterified with an ester group such as a (meth)acrylyl group. The term "(meth)acrylyl" is used herein to denote either acrylyl and/or methacrylyl moieties.
In Japanese patent No. 108480, there is disclosed how to make a graft copolymer by polymerizing a vinyl monomer in the presence of an APS difunctionalized with terminal double bonds. This is done by reacting the di-OH-terminated APS with an excess of methacryloyl chloride so that both ends of the APS are provided with methacrylyl chain ends. When reacted with the vinyl monomer, the structure of the resulting copolymer has a backbone of the polymerized vinyl monomer and methacrylyl chain ends from which backbone APS chains are pendant, the number of such chains depending upon the relative molar proportions of vinyl monomer and APS which are copolymerized. Each of the pendant APS chains has a terminal methacrylyl group which of course may react with additional vinyl monomer or another methacrylyl chain end forming a crosslinked network.
It will be clear that with the addition of an excess of methacryloyl chloride, there can be no APS chains with only a single methacrylyl chain end. As is well known, the reaction of methacryloyl chloride with a phenolic OH group is essentially quantitative amounting to a titration. Moreover, if even a trace quantity of APS chain ends were OH-terminated, they would function as an inhibitor for the subsequent polymerization with the vinyl monomer. Stated differently, the Japan reference was interested in functionalizing both chain ends directly with methacryloyl chloride and used an excess to make sure this occured. Thus the subsequent graft copolymer structure which was formed by polymerization with a vinyl monomer, resulted in pendant APS chains with methacrylyl chain ends which were free to react under the conditions of copolymerization.
I know of no instance where a sodium or potassium or other alkali metal salt of a APS, APK or PP oligomer has been prepared which is substantially insoluble in commonly available organic solvents at room temperature, yet has been used in a PTC reaction to esterify the oligomer with an ester chain end; or, a modified Williamson etherification to etherify the oligomer with a VB head ("styrene-type") chain end; either of which PTC reactions results in substantially 100% yield of the vinyl-functionalized macromer.
The process of my invention provides for such a reaction with a Pape oligomer. Such monofunctionalized macromers I have made are disclosed in Polymer Bulletin, Springer Verlag 1983, in two articles titled "Comb-Like Polymers and Graft Copolymers from Macromers" 1. Synthesis and Characterization of Methacrylate and Styrene Macromers of Aromatic Polyether Sulfones; and, 2. Synthesis, Characterization and Homopolymerization of a Styrene Macromer of Poly(2,6-Dimethyl-1,4-Phenylene Oxide); 10, 215-222, and 10, 397-403, respectively, by Virgil Percec, Peter L. Rinaldi and Brian C. Auman, the disclosures of which articles are incorporated by reference thereto as if fully set forth herein. More specifically, VB-terminated and (meth)acrylate-terminated macromers may be further polymerized or copolymerized rapidly to yield comb-like polymers or graft copolymers.
The monofunctionalized APS, APK and PPO macromers may also be used as intermediates for the synthesis of compounds with mono-ethynyl unsaturation. For example, the mono(styrenated) macromer may be converted to an .alpha.-(ethynylbenzyl) polysulfone or polyketone, either of which has a terminal triple bond. This macromer is a convenient starting material for the preparation of high temperature homopolymers and graft copolymers which cure thermally without generating volatiles.